1. Field of the Invention
The present invention relates to a display device using a light bulb that modulates the intensity of light, for example, a liquid crystal panel or a digital mirror device (DMD).
2. Description of the Prior Art
In recent years, Macrovision has been introduced into DVD (Digital Versatile Disc) software or the like in order to prevent copying for the purpose of protecting the copyright of the contents of a movie or the like. A Macrovision signal is superimposed on a vertical blanking period of a video signal, as shown in FIG. 4, and makes it impossible to normally record an output source by erroneously operating an AGC (Automatic Gain Control) in a video recording device.
In a case where the contents which have been subjected to copy protection by Macrovision are displayed by a liquid crystal projector, when the aspect ratio of an input signal and the aspect ratio of a liquid crystal panel differ from each other, the Macrovision signal superimposed on the vertical blanking period may, in some cases, be displayed as a video signal.
When the aspect ratio of the input signal is 4×3 (width×length), while the aspect ratio of the liquid crystal panel is 5×4 (width×length), for example, the video signal is written into the liquid crystal panel such that the width of the liquid crystal panel coincides with the width of the video signal. Accordingly, the length of the video signal is smaller than the length of the liquid crystal panel, so that the Macrovision signal superimposed on the vertical blanking period is written into the liquid crystal panel.